The field of the invention relates generally to the tracking and inventory of items on an aircraft, and more specifically, to methods and systems for real time RFID locating onboard an aircraft.
Existing inventory and tracking solutions based on active RFID and WiFi use signal strength measurements and time difference of arrival algorithms to determine location coordinates. More recently, broadband wireless location beacon signals have been used to overcome areas of poor WiFi coverage. One system uses a network of RFID readers and their dedicated processors and software to locate tags among a dedicated network of RFID readers. Another solution uses software controlled smart antennas to steer beams, and perform signal acquisition and source location using an array of elements, an array controller, plus an RFID reader module, weighing 50 to 85 lbs per antenna. Still another system requires placement of transmitters near tags and sophisticated signal processing to locate multiple tags with its long range phased array receiver.
Such systems have disadvantages and other limitations when applied to an aircraft environment. Specifically, such complex systems utilize components having significant weight or require significant computing resources for signal processing, which is always a concern or limitation in the aircraft environment. Although simpler system solutions can utilize active RFID tags, these active RFID tags are 1000 times more expensive per tag than passive RFID tags. Active RFID tags are at least one inch square in size, while passive RFID tags can be up to 1000 times smaller. Active RFID tags read by active RFID readers do have up to 100 times greater range than do passive RFID tags, when read by single passive RFID readers with single local transmit and receive antennas. However, the active RFID tags require tag batteries, and have very limited accuracy and resolution capabilities.
RFID systems that incorporate the less expensive passive RFID tags are complex, dedicated tracking solutions, with bulky and heavy smart antennas, as described above. Each tracking and communication solution requires a separate, dedicated wiring infrastructure. Digital networks of RFID tag readers have limited capabilities to estimate time difference of arrival for RFID tag location finding due to delays embedded in the digital network system solutions. Such delays are sometimes resolved through an array of networked short range passive RFID readers located at choke points though which the short range RFID tags pass to estimate real time locations of RFID tags.
There are aircraft applications that utilize active RFID technology, for example, to track aircraft parts and high value assets. Such applications are used primarily for intelligent inventory, and not location tracking.